Have you ever seen the massive exhaust tips on diesel pick-up trucks? They're so big because they mix outside air with the exhaust before discharging it That's because the exhaust gets so hot from the DPF burn-off that it'd burn off the truck's paint or anybody walking too close to the truck when it was parked and running.

There's a story about legendary NASCAR mechanic Smokey Yunick arguing with NASCAR inspectors about a gas tank of a car in the inspection bay being too big. Finally, Smokey had enough, threw the empty tank in the cockpit of car.. started the car up, and drove a half-mile back to his garage. (The car had plenty of gasoline in places they didn't find it.)